{"api_version":"1","generated_at":"2026-09-23T09:40:41+00:00","cve":"CVE-2026-81637","urls":{"html":"https://cve.report/CVE-2026-81637","api":"https://cve.report/api/cve/CVE-2026-81637.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-81637","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-81637"},"summary":{"title":"Replayable OAuth2 CSRF state retained after a failed callback in AshAuthentication","description":"Insufficient Session Expiration vulnerability in team-alembic AshAuthentication allows an attacker who obtains a victim's OAuth2 state value to replay the callback and sign that victim into an attacker-controlled account.\n\nAshAuthentication.Strategy.OAuth2.Plug.callback/2 clears the stored session_params through a rebinding step inside its with chain, conn <- delete_session(conn, session_key). Elixir evaluates the else block in the scope enclosing the with, so every failure path (the provider returning ?error=access_denied, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches store_authentication_result/2 holding the original connection and the session entry is never removed. The value the module's own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry.\n\nThis issue affects ash_authentication: from 0.6.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.","state":"PUBLISHED","assigner":"EEF","published_at":"2026-09-17 14:17:32","updated_at":"2026-09-18 18:16:18"},"problem_types":["CWE-613","CWE-613 CWE-613 Insufficient Session 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Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81637","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"team-alembic","product":"ash_authentication","version":"affected 0.6.0 4.15.0 semver","platforms":[]},{"source":"CNA","vendor":"team-alembic","product":"ash_authentication","version":"affected 5.0.0-rc.0 5.0.0-rc.14 semver","platforms":[]},{"source":"CNA","vendor":"team-alembic","product":"ash_authentication","version":"affected c5f589058e04239263f50a1430eb17ea6d5dd1a2 * git","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[{"source":"CNA","value":"Peter Ullrich","lang":"en"},{"source":"CNA","value":"Jonatan Männchen / EEF","lang":"en"},{"source":"CNA","value":"James 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Ullrich"},{"lang":"en","type":"analyst","value":"Jonatan Männchen / EEF"},{"lang":"en","type":"remediation developer","value":"James Harton"}],"dateAssigned":"2026-09-11T18:16:32.000Z","descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"<p>Insufficient Session Expiration vulnerability in team-alembic AshAuthentication allows an attacker who obtains a victim's OAuth2 <code>state</code> value to replay the callback and sign that victim into an attacker-controlled account.</p>\n<p><code>AshAuthentication.Strategy.OAuth2.Plug.callback/2</code> clears the stored <code>session_params</code> through a rebinding step inside its <code>with</code> chain, <code>conn &lt;- delete_session(conn, session_key)</code>. Elixir evaluates the <code>else</code> block in the scope enclosing the <code>with</code>, so every failure path (the provider returning <code>?error=access_denied</code>, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches <code>store_authentication_result/2</code> holding the original connection and the session entry is never removed. The value the module's own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry.</p>\n<p>This issue affects ash_authentication: from 0.6.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.</p>"},{"base64":false,"type":"text/markdown","value":"Insufficient Session Expiration vulnerability in team-alembic AshAuthentication allows an attacker who obtains a victim's OAuth2 `state` value to replay the callback and sign that victim into an attacker-controlled account.\n\n`AshAuthentication.Strategy.OAuth2.Plug.callback/2` clears the stored `session_params` through a rebinding step inside its `with` chain, `conn <- delete_session(conn, session_key)`. Elixir evaluates the `else` block in the scope enclosing the `with`, so every failure path (the provider returning `?error=access_denied`, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches `store_authentication_result/2` holding the original connection and the session entry is never removed. The value the module's own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry.\n\nThis issue affects ash_authentication: from 0.6.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14."}],"value":"Insufficient Session Expiration vulnerability in team-alembic AshAuthentication allows an attacker who obtains a victim's OAuth2 state value to replay the callback and sign that victim into an attacker-controlled account.\n\nAshAuthentication.Strategy.OAuth2.Plug.callback/2 clears the stored session_params through a rebinding step inside its with chain, conn <- delete_session(conn, session_key). Elixir evaluates the else block in the scope enclosing the with, so every failure path (the provider returning ?error=access_denied, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches store_authentication_result/2 holding the original connection and the session entry is never removed. The value the module's own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry.\n\nThis issue affects ash_authentication: from 0.6.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14."}],"impacts":[{"capecId":"CAPEC-60","descriptions":[{"lang":"en","value":"CAPEC-60 Reusing Session IDs (aka Session 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Elixir evaluates the else block in the scope enclosing the with, so every failure path (the provider returning ?error=access_denied, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches store_authentication_result/2 holding the original connection and the session entry is never removed. The value the module's own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry.\n\nThis issue affects ash_authentication: from 0.6.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.","Type":"Description","Title":"Replayable OAuth2 CSRF state retained after a failed callback in"}]}}}